The present invention relates to a composite film formed by coating aligned carbon nanotubes with a polymer, and to a sensor which incorporates the polymer-carbon nanotube composite film.
Chemical vapor sensors are widely used in applications such as defense, homeland security, health care, and environmental monitoring applications. For example, chemical vapor sensors may be used for real-time sensing of chemical warfare stimulants in a battlefield by monitoring resistivity changes of soldiers' clothing. In recent years, there has been an increasing need for chemical vapor sensors which are efficient, mechanically robust, environmentally stable, and which operate with low power consumption.
Chemical vapor sensors are known which are based on conjugated conducting polymers. Such polymers exhibit the optoelectronic properties of inorganic semiconductors or metals. However, the poor environmental stability associated with most conjugated polymers has precluded their use in practical applications.
Carbon nanotubes have been shown to possess similar optoelectronic properties to that of conjugated polymers. Unlike conjugated polymers, carbon nanotubes are environmentally stable due to their seamless arrangement of hexagon rings without a dangling bond. In addition, their high surface area and small size make carbon nanotubes an attractive candidate for use in chemical vapor sensors. The use of non-aligned carbon nanotubes has been used for detecting gaseous materials, where the detection of gases is achieved by measuring the change in electrical properties of the carbon nanotubes induced by the charge transfer with the gas molecules (e.g., O2, H2, CO2) or by the capacitor change due to physical adsorption of the gas molecules. However, the number of analytes which can be detected using such a carbon nanotube-based sensor is hampered by the limited specific interactions and transduction mechanisms employed.
Accordingly, there is still a need in the art for a chemical vapor sensor which exhibits environmental stability, which exhibits good optoelectronic properties, and which can easily detect a wide variety of analytes.